Cooperative LBT Design and Effective Capacity Analysis for 5G NR Ultra Dense Networks in Unlicensed Spectrum

Song, Hengguo; Cui, Qimei; Gü, Yü; Stuber, G.L.; Li, Yong; Fei, Zesong; Guo, Chongtao

doi:10.1109/access.2019.2910582

Cited by 28 publications

(23 citation statements)

References 26 publications

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“…As the greenfield 6 GHz bands provide an opportunity to investigate and design coexistence mechanisms from the ground up, coexistence between unlicensed RATs in the 6 GHz bands need not consider the CSMA/CA-like LBT mechanisms as the baseline. Although such modified LBT-based mechanisms have been proposed in the literature (e.g., [110]), at the time of writing this paper the LBT mechanism used in Wi-Fi and LTE-LAA continues to be the baseline for 6 GHz operations. In what follows, we describe key considerations that will govern the performance of all unlicensed RATs operating and coexisting in the 6 GHz bands.…”

Section: A Channel Access Protocolmentioning

confidence: 99%

Next Generation Wi-Fi and 5G NR-U in the 6 GHz Bands: Opportunities and Challenges

et al. 2020

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The ever-increasing demand for unlicensed spectrum has prompted regulators in the US and Europe to consider opening up the 6 GHz bands for unlicensed access. These bands will open up 1.2 GHz of additional spectrum for unlicensed radio access technologies (RATs), such as Wi-Fi and 5G New Radio Unlicensed (NR-U), in the US and if permitted, 500 MHz of additional spectrum in Europe. The abundance of spectrum in these bands creates new opportunities for the design of mechanisms and features that can support the emerging bandwidth-intensive and latency-sensitive applications. However, coexistence of unlicensed devices both with the bands' incumbent users and across different unlicensed RATs present significant challenges. In this paper, we provide a comprehensive survey of the existing literature on various issues surrounding the operations of unlicensed RATs in the 6 GHz bands. In particular, we discuss how key features in next-generation Wi-Fi are being designed to leverage these additional unlicensed bands. We also shed light on the foreseeable challenges that designers of unlicensed RATs might face in the near future. Our survey encompasses key research papers, contributions submitted to standardization bodies and regulatory agencies, and documents presented at various other venues. Finally, we highlight a few key research problems that are likely to arise due to unlicensed operations in the 6 GHz bands. Tackling these research challenges effectively will be critical in ensuring that the new unlicensed bands are efficiently utilized while guaranteeing the interference-free operation of the bands' incumbent users. INDEX TERMS 6 GHz unlicensed spectrum, IEEE 802.11ax, IEEE 802.11be, 5G NR-U. I. INTRODUCTION Wireless devices operating in unlicensed bands have become an integral part of our lives today. The Federal Communications Commission (FCC) in the US first opened up the 2.4-2.4835 GHz and 5.725-5.85 GHz bands for unlicensed access in 1985 [1]. Since then, several unlicensed radio access technologies (RATs)-most notably IEEE 802.11based Wi-Fi, Bluetooth, and ZigBee-have been developed that can not only operate in these bands but also coexist with each other. The 2.4 GHz band, referred to as the Industrial, Scientific, and Medical (ISM) band, is open for unlicensed access worldwide, while unlicensed RATs such as Wi-Fi are allowed to operate in several portions of the 5 GHz bands in most regions across the world [2]. In the US, these 5 GHz bands are referred to as the Unlicensed National Information Infrastructure (U-NII) bands. Wi-Fi is arguably the most popular unlicensed RAT that provides mobile and high-speed Internet access over wireless local area networks (WLANs). Wi-Fi devices are ubiquitous in today's home and enterprise wireless networks, with an estimated 9.5 billion devices in use [3]. Furthermore, with the growing popularity of emerging applications such as wireless augmented reality (AR), virtual reality (VR), and mobile gaming, the demand for Wi-Fi-based high-throughput, highreliability and low-laten...

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Section: A Channel Access Protocolmentioning

confidence: 99%

Next Generation Wi-Fi and 5G NR-U in the 6 GHz Bands: Opportunities and Challenges

et al. 2020

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“…In particular, an important issue is the coexistence problem with other communication devices such as Wi-Fi. In [7], [8], the authors improve coexistence performance by modifying the LBT operation. However, these papers focus only on the DL performance of LTE.…”

Section: A Related Workmentioning

confidence: 99%

“…After measuring inter-packet intervals, the eNB determines whether the channel is saturated or not. Transmission of some consecutive packets is considered a 'packet burst' if interpacket intervals are in the range of [DIFS, AIFS+15×σ], 7 where AIFS stands for arbitration inter-frame space. This range includes most inter-packet transmission intervals when packets are continuously transmitted with LBT operation.…”

Section: ) Channel Saturation Detectionmentioning

confidence: 99%

“…Therefore, each UE has 1 ms to occupy the channel before its scheduled UL transmission. 7 We do not consider SIFS as an inter-packet interval. If an inter-packet interval is point coordination function inter-frame space (PIFS), we exclude the following packet length from the calculation because it is an intermittent packet such as Wi-Fi beacon.…”

Section: ) Delayed Schedulingmentioning

confidence: 99%

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Uplink Channel Access Enhancement for Cellular Communication in Unlicensed Spectrum

Kim

Bahk

2020

IEEE Access

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3GPP cellular communications in unlicensed spectrum allow transmission only after completing listen-before-talk (LBT) operation. For downlink, the LBT operation helps cellular traffic to coexist well with Wi-Fi traffic. However, cellular uplink transmission is attempted only at the time specifically determined by the base station after having a successful LBT and the user equipment (UE) may suffer transmission failure and delayed transmission due to Wi-Fi interference. As a result, cellular uplink traffic does not coexist well with Wi-Fi traffic. This paper mathematically analyzes the problem of unfairness between cellular and Wi-Fi for uplink channel access. To address the coexistence problem in unlicensed spectrum, we propose a standard-compliant approach, termed UpChance, which allows the UE to use a minimum length of uplink reservation signal and the base station to determine the optimal timing for the UE's uplink transmission. Through ns-3 simulation, we verify that UpChance improves the performance of fairness and random access completion time by up to 88% and 99%, respectively.

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“…Thus, LTE has been recently deployed to operate over unlicensed bands providing enhanced mobile networks capacities [3], [4]. This same concept is likely to be introduced as well in the future 3GPP specification for 5G New Radio Unlicensed (5G NR-U) and therefore still constitutes a research topic of recent interest [5], [6].…”

Section: Introductionmentioning

confidence: 99%

Novel LAA Waiting and Transmission Time Configuration Methods for Improved LTE-LAA/Wi-Fi Coexistence Over Unlicensed Bands

Alhulayil

López-Benítez

2020

IEEE Access

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Long Term Evolution-Licensed Assisted Access (LTE-LAA) has been pointed out as a key solution to cope with the increasing amounts of data traffic and the scarcity of the licensed spectrum. The 3rd Generation Partnership Project (3GPP) has standardised LAA to operate over the 5 GHz unlicensed spectrum which is mainly occupied by Wi-Fi. It is a challenging problem to ensure a fair coexistence between these technologies. Several studies have been proposed in the literature to allow a fair LAA/Wi-Fi coexistence. In this work, various methods are proposed to adapt/select the waiting times for LAA based on the activity statistics of the existing Wi-Fi network. The main novelty is that the knowledge of the existing Wi-Fi activities is exploited to tune the boundaries of the Contention Window (CW) for LAA and to select fixed waiting times for LAA. Moreover, a dynamic method is proposed to adapt the Transmission Opportunity (TxOP) times for LAA based on the Hybrid Automatic Repeat Request (HARQ) feedbacks. The methods are evaluated using ns-3 network simulator based on the 3GPP fairness definition. We show that selecting fixed waiting times for LAA based on the existing Wi-Fi activities is more friendly to the existing Wi-Fi and provides better total aggregated throughputs for both coexisting networks compared to the 3GPP Category 4 Listen Before Talk (Cat 4 LBT) algorithm. Moreover, the proposed dynamic TxOP method is more friendly to the existing Wi-Fi and provides better total aggregated throughputs compared to the fixed TxOP period approach of the 3GPP Cat 4 LBT scheme. INDEX TERMS Licensed assisted access, LTE/Wi-Fi coexistence, ns-3, Unlicensed spectrum, Wi-Fi.

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Cooperative LBT Design and Effective Capacity Analysis for 5G NR Ultra Dense Networks in Unlicensed Spectrum

Cited by 28 publications

References 26 publications

Next Generation Wi-Fi and 5G NR-U in the 6 GHz Bands: Opportunities and Challenges

Next Generation Wi-Fi and 5G NR-U in the 6 GHz Bands: Opportunities and Challenges

Uplink Channel Access Enhancement for Cellular Communication in Unlicensed Spectrum

Novel LAA Waiting and Transmission Time Configuration Methods for Improved LTE-LAA/Wi-Fi Coexistence Over Unlicensed Bands

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